Spinal fixation systems typically require the threaded securement of some form of bone anchor and the like or bone screw-assembly into two or more vertebrae, as well as the which requires the drawing of the rod to the anchors/screw-assemblies, or drawing the anchors/screw-assemblies to the rod.
Typically, these procedures are performed by a surgeon using separate tools. By way of example, Applicant has previously developed a new variable angle spinal screw-assembly that provides adjustable securement of a stabilization rod between at least two vertebrae to effect internal fixation of the spine across those vertebrae (co-pending U.S. patent application Ser. No. 10/848,946, filed May 19, 2004, the entire disclosure herein incorporated by reference). As indicated above, this spinal screw-assembly is used with at least one other such assembly to secure a stabilization rod and includes a pedicle screw, a body member and a locking cap. The pedicle screw may include a substantially spherical or elliptical head portion defining a slot therein used to drive the threaded shaft portion of the screw into a vertebrae. The body member of the screw assembly is generally cylindrical in configuration and adapted to receive the head portion of the pedicle screw and cooperate therewith so as to define a modified ball-joint. This design allows for variable angular movement of the body member with respect to the pedicle screw with the threaded shaft portion of the screw extending through an opening in the end of the body member.
The body member additionally preferably defines a pair of opposed parallel slots (or a single slot or receiving an end of a rod) axially disposed in the side wall thereof forming a saddle to receive a portion of the cylindrical fixation rod. A set screw is used to threadably engages the body member of the screw assembly to secure the stabilizing rod within the body member.
A screw driver may be used to tighten the set screw, while a separate tool is necessary to either draw the fixation rod down into the opposed slots in the body member of the screw assembly or, when necessary, to draw the pedicle screw and attached vertebrae outwardly to the rod to effect the desired alignment of the vertebrae and the securement of the rod.